The present invention relates to a system for preventing collision of a vehicle.
For the purpose of preventing collision of a vehicle against an obstacle, it has been the practice to mount a radar system on a vehicle to detect the relative distance and relative speed between the vehicles or between a vehicle and an obstacle. As the radar system is mounted on the vehicle, a single antenna system capable of transmitting and receiving the waves is more preferable than a system utilizing a plurality of antennae in view of the mounting space of the antenna, and a pulse radar system has been generally used because of its high accuracy of measuring distance. In the single antenna type pulse radar system, for the purpose of preventing the saturation phenomena in the receiving amplifier caused by a signal leaked from the transmitting system to the receiving system, the receiving sensitivity is intentionally decreased during about 2 to 3 times of the pulse width starting from the instant of transmitting a pulse. Therefore, where the time required for the pulse to reach a target is shorter than this interval, the reflected signal will be completely eliminated thus establishing a so-called blind zone in which the radar system cannot detect the target.
In this manner, when a vehicle approaches an obstacle and comes into a blind zone, the prior art radar system misses the obstacle so that it cannot detect such target informations as the distance to the obstacle and the relative speed between the vehicle and the obstacle. Accordingly, a braking signal for commanding the braking operation of the vehicle is interrupted so that the brake will be inadvertently released whereby the vehicle collides against the obstacle at a speed with which the vehicle has entered into the blind zone.